Coffmann cartridge composition?
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Coffmann cartridge composition?
Anyone know where I can find out the recipe for the composition of a Coffmann cartridge for an Auster AOP IX?
Thanks,
QDM
Thanks,
QDM
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QDM,
Remember the Coffmans well from Chipmunk days.
Not the kind of thing you could sit and make on you kitchen table !
Seeing rows of a dozen Chipmunks all starting up to be ferried to the University air sqadrons was like WW III !
The breech held six and we would stand by with spare breech barrels ready loaded.
Problems were not only the engine not starting ( too weak or too rich) but dud cartridges that gave smoke but no fire
There is a conversion from Coffman to electric but may no help if you dont have an electrical system
Remember the Coffmans well from Chipmunk days.
Not the kind of thing you could sit and make on you kitchen table !
Seeing rows of a dozen Chipmunks all starting up to be ferried to the University air sqadrons was like WW III !
The breech held six and we would stand by with spare breech barrels ready loaded.
Problems were not only the engine not starting ( too weak or too rich) but dud cartridges that gave smoke but no fire
There is a conversion from Coffman to electric but may no help if you dont have an electrical system
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Not the kind of thing you could sit and make on you kitchen table !
Anyone know the composition?
QDM
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I'll post this with a disclaimer - Nopax accepts NO RESPONSIBILITY WHATSOEVER for any damage you may do to yourself or others.
Have you got an old cartridge? When I was at Cambridge airport we took one apart out of curiosity - it appeared to be a standard shotgun cartridge, except that the shot was replaced with cut-up pieces of propellant. The propellant itself was in a solid disc about 1/2 inch thick at the base of the cartridge. So I guess it would be possible to make one by using the 'cooking' version, removing the shot, and replacing it with lumps of propellant, about 1/4 inch cubes, if memory serves. Of course this is based upon the wild assumption that the propellant is the same composition in both versions. Maybe a cartridge manufacturer could make one for you?
As a minor aside, I believe that the correct spelling is 'Koffman', but as far as web searches are concerned, there are as many 'C's as 'K's
Either way, I wouldn't want to be near one for the first test....
Have you got an old cartridge? When I was at Cambridge airport we took one apart out of curiosity - it appeared to be a standard shotgun cartridge, except that the shot was replaced with cut-up pieces of propellant. The propellant itself was in a solid disc about 1/2 inch thick at the base of the cartridge. So I guess it would be possible to make one by using the 'cooking' version, removing the shot, and replacing it with lumps of propellant, about 1/4 inch cubes, if memory serves. Of course this is based upon the wild assumption that the propellant is the same composition in both versions. Maybe a cartridge manufacturer could make one for you?
As a minor aside, I believe that the correct spelling is 'Koffman', but as far as web searches are concerned, there are as many 'C's as 'K's
Either way, I wouldn't want to be near one for the first test....
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NoPax,
The main part of the cartridge is the stick of cordite and at the striker end there is the standard shotgun cartridge percussion cap.
Between the two there was a collection of what looked like large rat **** that are called the fast burners.
The percusion cap is not sufficient to get a steady burn so the fast burners got it all going.
Took many apart as an aprenti and the party trick was to take a screw top tobacco tin, drill some 1/8 th holes in the base and the sides. pulling the side holes in radial direction.
The Coffman cartridge was then dismantled the fast burners laid on the bottom of the tin with cordite chopped up with a penknife and put on top. The top was firmly screwed on, the tin was set between two bricks, a pice of petrol soaked rag was put between the bricks, a match thrown and RUN !!
Very spectacular ( accompanied by a banshee scream !) with some quite extended "flights "
Definitely livened up a lunch time !
Until banned by management
The main part of the cartridge is the stick of cordite and at the striker end there is the standard shotgun cartridge percussion cap.
Between the two there was a collection of what looked like large rat **** that are called the fast burners.
The percusion cap is not sufficient to get a steady burn so the fast burners got it all going.
Took many apart as an aprenti and the party trick was to take a screw top tobacco tin, drill some 1/8 th holes in the base and the sides. pulling the side holes in radial direction.
The Coffman cartridge was then dismantled the fast burners laid on the bottom of the tin with cordite chopped up with a penknife and put on top. The top was firmly screwed on, the tin was set between two bricks, a pice of petrol soaked rag was put between the bricks, a match thrown and RUN !!
Very spectacular ( accompanied by a banshee scream !) with some quite extended "flights "
Definitely livened up a lunch time !
Until banned by management
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GotTheShirt
I've heard of these before and also ones made from a slice of the cordite in a Canberra starter cartridge. Pop them on the barbie at a squadron party and it makes the whole thing go with a bang!
I've heard of these before and also ones made from a slice of the cordite in a Canberra starter cartridge. Pop them on the barbie at a squadron party and it makes the whole thing go with a bang!
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OK, assuming that you are operating/restoring an AOP 9, then you would not want to be using out-of-date pyrotechnics; if there's no way to make it electric start, or you want to keep her original, why not speak to the Army's historic flight (01342 810736 or 01327 62664) to see what they do. They run a pair of AOP 9's so they must have some good contacts (if you'll excuse the pun)
There's also the Auster club, but I reckon they would just recommend that you don't use a cartridge starter anyway.
Good luck!
There's also the Auster club, but I reckon they would just recommend that you don't use a cartridge starter anyway.
Good luck!
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Used to fly the cartridge powered Chippie for glider towing etc. Someone once told me that the cartridges were about 9 times as powerful as the normal 12 bore jobs. Hence when we took 6 Chipmunks to France, had to fly the cartridges in the stowage rather than keep them all together in our sea-borne transport. V dangerous if they all go up together on the car deck (also dodgy if 30 odd go up behind you, but that's another matter). Point is, be very careful.
